Many laminate materials, such as labels, are initially placed on a release liner prior to application to a product or to another substrate. The release liners can be made from polymer films. For instance, in one embodiment, the release liner may comprise a silicone-coated polyester film. Such silicone-coated films are commonly employed as release liners for labels, pressure sensitive tapes, decorative laminates, transfer tapes, and the like. The silicone coating on the base polymer film allows the adhesive face of the laminate material to be easily removed from the film prior to use.
Release liners made from polymer films, such as polyester films, have become commercially successful and are used in great quantities. Unfortunately, however, the release liners made from polymer films are typically only used once and then discarded. To date, no entity has been commercially successful in recycling the used liner material. In fact, most spent release liner ends up in landfills. It is estimated that over 35 million pounds per year of spent release liner enters the waste stream only after a single use. The above numbers are especially troubling in that the release liner is only a collateral material used to temporarily hold a label or other laminate material and is not itself incorporated in to the resulting product.
Although there is a need in the art to develop a way to recycle or to reuse spent release liner, various obstacles exist that have made reusing spent release liner problematic. For instance, spent release liner, especially liner made from polyester film, is not well suited for being reprocessed and formed back into a film product. The polyester contained in the release liner, for instance, has a tendency to degrade and possess inferior optical and mechanical properties making it very difficult to reuse the material in significant quantities. For instance, polyester film has a tendency to absorb moisture causing a substantial loss of molecular weight as indicated by a measured decrease in intrinsic viscosity. The molecular weight of the polymer decreases to an extent that the polymer can no longer be processed in commercial equipment and reformed into a film. In addition, reprocessed polyester tends to undergo significant yellowing and has increased haze making the resulting film undesirable to customers.
Another problem in recycling spent release liner is the ability to collect the material once it has been used. Release liner, for instance, goes through an extended supply chain making it difficult for the material to be recovered. For instance, the polyester film is typically manufactured by a film maker and then sent to a laminator. The laminator applies a laminate facestock material to the film. The laminate material is then sent to a printer and converter who then prints and diecuts the labels on the release liner. From the printer and the converter, the laminate material is then sent to an end user who typically has no relationship to the original film maker. The end user removes the labels from the release liner and discards the liner to a landfill or otherwise is sold as scrap material and exported to developing countries. Further, even if the film maker wanted to collect the spent release liner and had access to the material, the used release liner is typically combined with other industrial waste and scraps.
In view of the above, a need currently exists for a process for collecting spent release liner and for a process to reuse the liner that overcomes the above noted problems and drawbacks.